If I cut out a 20 second chunk from each track, starting from about 1:25, using Audacity, would it negatively affect the samples at all? I want to be able to easily play the same chunk of music from each track quickly back and forth.

_________________________
"I wish I had documented more…" said nobody on their death bed, ever.

I have another idea. Could you randomly -- and by randomly, I mean assign digits 1 through n to the different versions of the track -- string together 15-second cuts of different tracks so that you're left with a seamless track that smoothly transitions between bit-rates?

The overall goal would be for the listener to identify which 15 second spans are encoded with the highest quality, starting at time index 0:00, 0:15, 0:30, etc. Since you'd assign the parts randomly, you may end up with a few consecutive spans of the same quality. With the chunks only being 15 seconds long, you'd also increase your chances of using all the bit-rates before the end of the track.

_________________________
"I wish I had documented more…" said nobody on their death bed, ever.

Very good, Chris. Although my previous personal experience and study of other test results didn't leave much doubt that both 320 kbps CBR or the "extreme"VBR(around mid 200s kbps)would be audibly transparent(even with about 80% of the audio data discarded), I listened on both speakers and headphones.

I paid special attention to the first 12 seconds before the singing attempt began, particularly the 9th though 12th notes, which have the sort of content which might demonstrate a difference. After several trials on each of the four samples, nothing was heard would support anything beyond a pure guess.

This might be surprising to some who claim to be able to hear a difference even between pieces of connecting wire, but it's the reality of modern audio technology.

This has been interesting. We looked at bit depth, what about sampling rate?

I can try something with sampling rate. But while I'm sure of 0-filling LSBs, in order to make the files the same size. I'd have to take a higher sampling rate, and downsample it, and then upsample it again, and that may not be as clear cut.

I'll play around, and see if there are any extremely obvious tell-tale signs that would make the test inaccurate.

If I cut out a 20 second chunk from each track, starting from about 1:25, using Audacity, would it negatively affect the samples at all? I want to be able to easily play the same chunk of music from each track quickly back and forth.

No, nothing wrong with doing that. Of course it's also possible to use Audacity to cheat, but you won't do that, right?

As for identifying 15 second segments of one track. I can do that. In fact I was flipping between bit-depths as I was preparing the test. I could identify 8 and 12-bit, but 16-, 20-, and 24-bit all sounded the same to me. I'm just not that sure of how good a test it would be. It's hard to say, "this is 16-bit," without having something to compare against.

I paid special attention to the first 12 seconds before the singing attempt began, particularly the 9th though 12th notes, which have the sort of content which might demonstrate a difference. After several trials on each of the four samples, nothing was heard would support anything beyond a pure guess.

Yeah. And as I've said, that first test was really absolutely worse case, and I couldn't tell the difference.

Did you check out the second set of tracks? (You might like the music too.) I'm glad that I had the option for 8- and 12-bit output, or I would have never believed that the dithering software I was using was even doing anything (actually, I can see it doing something on the VU meter at the higher depths, but I can't hear it).

Oh, and a fun fact. I was going to use a track from R.E.M. for this second test, but as I was processing it, my digital clip indicator came on. This is why we can't have nice things, the engineer was given 24-bits and he still slammed it into a brick wall. (Although it's no were near as bad as The Flaming Lips', At War with the Mystics.)

Okay, I listened to the Carmina Burana samples(Thielemann?). Quite dynamic, but nothing that can't be handled easily with 16 bits. The dynamic range on all was about 50dB, from the upper 50s to a max of 106dB on my SPL meter, and sounded identical.